Reaper was introduced in Endwalker and has an Endwalker relic. We're just only at the first stage so far. Other jobs didn't get relics from previous expansions either. They get current content and new content going forward. It's no different for other jobs. The Omega Reaper weapon was recently added simply because it's the base model for Ultimate.

The same applies to other gear. Reaper didn't exist prior to this expansion, so there is no previous Reaper-themed gear. It shares Maiming gear with Dragoon.

Also, you say "not even realistic to what historically reaper or scythe users in general would actually wear". Are you asking to dress like a farmer?